1. Field of the Invention
The present invention relates generally to a composite automobile component and the method of making that automobile component. More particularly, the present invention relates to a fuel tank which includes a shield to protect the fuel tank from heat generated from other engine components and a method of making the shielded fuel tank in situ while blow-molding the fuel tank in a mold. Even more particularly, the present invention relates to a shield attached to a blow-molded component so as to create a plurality of air gaps therebetween.
2. Description of the Related Art
In the past, fuel tanks have been made from metal, more particularly steel. Steel is relatively impervious to damage from many of the road hazards present, namely rocks, potholes, and the like. Also, steel will not deform or degrade in the presence of heat radiated from other components of the automobile, such as the exhaust system, which are located near the fuel tank.
More recently, however, it has become desirable to decrease the weight of vehicles to achieve better fuel efficiency, among other reasons. To decrease the weight, modifications have been made to many of the components of vehicles, including the fuel tank. The fuel tanks have begun to be made from lighter, less expensive materials, such as aluminum and plastics. However, a problem has arisen with the use of plastic in particular as the material from which the fuel tank is made.
A primary problem with substituting plastic for steel in the fuel tank is that, as mentioned earlier, there are components which radiate heat located near the fuel tank. Because plastic has a lower melting temperature than steel, the plastic fuel tank is more likely to degrade or rupture from the heat generated by the heat-radiating components, particularly the exhaust system, opposed to the steel fuel tank. As a result, it is necessary to provide some sort of shielding on or near the plastic fuel tank to reduce the heat transmitted to the fuel tank.
One option in preventing heat transmission is to install a heat shield between the exhaust system and the fuel tank. A variety of types of heat shields have been used in automobiles to shield components from heat. One example is found in the patent to Butler, U.S. Pat. No. 5,656,353. However, with the Butler shield as with others, the shield must be spaced from each of the heat-radiating component and the component the shield protects. In the context of the fuel tank and exhaust, the space limitations, such as requirements for clearance of the exhaust from the ground, prohibit the degree of spacing required by the Butler shield. A shield which is formed integrally with the fuel tank is, therefore, preferable.
An example of one attempt to provide a shield for a plastic fuel tank is disclosed in the patent to Stiles et al., U.S. Pat. No. 5,188,981. Stiles describes a structure which includes a number of layers. Most particularly, Stiles describes a fuel tank made of a thermoformable material and including a localized heat shield. However, in the Stiles reference, it is critical that the heat shield material and thermoformable material be selected such that the thermoformable material can penetrate into a portion of the heat shield material. This necessary characteristic limits the materials from which the heat shield and the fuel tank may be made.
The structures previously used do not allow for sufficient flexibility in the materials used to create the shield and are limited relative to their position with respect to the shielded and heat-generating components. Nor do these prior systems provide sufficient flexibility to permit their use as shields over more than a relatively limited area of a fuel tank which may be desirable to shield the fuel tanks from other road hazards, such as rocks, potholes, and the like. The present invention provides an alternative which more satisfactorily fulfills these highly desirable objectives.
An invention related to the present invention, entitled HEAT SHIELDS FOR BLOW-MOLDED COMPONENTS AND METHOD OF MAKING was filed in the U.S. Patent and Trademark Office on Oct. 19, 1998, and has been given Serial No. 09/175,398 now abandoned. The invention disclosed and claimed in that application may be modified to achieve a different result from the result garnered without the modifications disclosed and claimed in the present invention. The disclosure in the above-mentioned application is incorporated herein by reference.